1. Field of the Invention
The present invention relates to technology for electrically connecting terminals of an IC chip to a conductive layer disposed in a substrate.
2. Description of the Related Art
With respect to IC (integrated circuit) chips, bus sizes are being expanded and analog functions are being disposed in accompaniment with an increase in high speed processing in recent years. Thus, the number of terminals such as ground terminals or power terminals is increasing, and costs and package sizes are becoming large. For this reason, as shown in FIG. 7, as a connection structure for connecting, to a circuit substrate, a package in which an IC chip is sealed, there is a connection structure that uses a lead frame (conductive portion) 82 of a lead 81 derived from a package 80 as a ground layer (see Japanese Patent Application Laid-Open Publication (JP-A) No. 7-249724).
That is, in the connection structure shown in FIG. 7, the lead 81 is connected by solder 85 to a signal-use land (pad) 86 disposed on a circuit substrate 90, and the lead frame 82 is connected by the solder 85 to a ground-use pad 88 disposed on the circuit substrate 90. Also, in the connection structure shown in FIG. 7, a dielectric member 83, which is formed by an insulating film that prevents electromagnetic interference between adjacent leads, is disposed between the lead 81 and the lead frame 82. Moreover, plural thermal vias (through-holes filled with a metal) 84 are formed below the ground-use pad 88 in the circuit substrate 90.
Because the lead frame 82 is used as a ground layer in the connection structure shown in FIG. 7, a ground connecting lead becomes unnecessary and, as a result, the number of lead pins can be reduced. Also, because the ground-use pad 88 is connected to the thermal vias 84 in the connection structure shown in FIG. 7, the heat-radiating effect is improved.
However, in the connection structure described in JP-A No. 7-249724, it is necessary to superpose the lead 81, the dielectric member (insulating film) 83 and the lead frame 82 in order to use the lead frame 82 as a ground layer. Therefore, in the conventional example shown in FIG. 7, because the terminal structure around the lead 81 becomes complex and minute, costs increase and packaging labor becomes difficult.